1. Field of the Invention
The invention relates to a wireless sensor network (WSN) system, and more particularly to a WSN system awakened by utilizing a light.
2. Related Art
The wake-up mechanism in present wireless sensor network systems is mainly dependent on a singular wake-up mechanism. When a node of the wireless sensor network system enters a sleeping state, the receiving device of the node must be in an awake state in order for the node to be awakened through radio-frequency signal.
However, the wake-up mechanism triggered through radio frequency signal is power-consumptive. The wireless sensor network system deployed at a location without power outlets are usually powered by batteries. High power consumption at the wireless sensor network system may easily result in battery depletion. When the wireless sensor network system has no remaining battery capacity, the wireless sensor network system becomes disconnected and end devices become unable to communicate to the coordinator.